South African Class 6E1, Series 7

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South African Class 6E1, Series 7
SAR Class 6E1 Series 7 E1807.JPG
No. E1807 at Kaalfontein, 23 September 2009
Type and origin
Power type Electric
Designer Union Carriage & Wagon
Builder Union Carriage & Wagon
Model UCW 6E1
Build date 1977-1979
Total produced 150
UIC classification Bo-Bo
Gauge 3 ft 6 in (1,067 mm) Cape gauge
Bogies 3.430 m (11 ft 3 in) wheelbase
Wheel diameter 1,220 mm (48 in)
Wheelbase 11.279 m (37 ft 0.1 in)
Length 15.494 m (50 ft 10 in)
Width 2.896 m (9 ft 6 in)
Height 4.089 m (13 ft 5 in) pantographs down
Axle load 22,226 kg (21.9 long tons)
Locomotive weight 88,904 kg (87.5 long tons)
Current collection
Traction motors Four AEI 283 AY
Transmission 18/67 gear ratio
Performance figures
Maximum speed 113 km/h (70 mph)
Power output Per motor:
623 kW (835 hp) 1 hour
563 kW (755 hp) continuous
2,492 kW (3,342 hp) 1 hour
2,252 kW (3,020 hp) continuous
Tractive effort 311 kN (70,000 lbf) starting
221 kN (50,000 lbf) 1 hour
193 kN (43,000 lbf) continuous at 40 km/h (25 mph)
Locomotive brake Air & Regenerative
Train brakes Air & Vacuum
Operator(s) South African Railways
Transnet Freight Rail
Class Class 6E1
Power class 3 kV DC
Number in class 150
Number(s) E1746-E1895 [1]
Delivered 1977-1979
First run 1977

The South African Class 6E1, Series 7 of 1977 is a South African electric locomotive from the South African Railways era.

Between 1977 and 1979 the South African Railways placed one hundred and fifty Class 6E1, Series 7 electric locomotives with a Bo-Bo wheel arrangement in mainline service.[1]


The 3 kV DC Class 6E1, Series 7 electric locomotive was designed and built for the South African Railways (SAR) by Union Carriage and Wagon (UCW) in Nigel, Transvaal. The electrical equipment was supplied by the General Electric Company (GEC).[2]

One hundred and fifty locomotives were delivered between 1977 and 1979, numbered in the range from E1746 to E1895. UCW did not allocate builder’s or works numbers to the locomotives it built for the SAR and used the SAR unit numbers for their record keeping.[1]



The Class 6E1 was built with sophisticated traction linkages on their bogies and with stabilisers mounted between the linkages on the bogies and the locomotive body. Together with its electronic wheelslip detection system, these traction linkages and stabilisers ensure the maximum transfer of power to the rails without causing wheelslip.[3]


SAR Class 6E1 Series 7 E1862 BP.JPG

These dual cab locomotives have a roof access ladder on one side only, just to the right of the cab access door. The roof access ladder end is marked as the number 2 end. A passage along the centre of the locomotive connects the cabs, which are identical apart from the fact that the handbrake is located in cab 2. A pantograph hook stick is stowed in a tube mounted below the lower edge of the locomotive body on the roof access ladder side. The locomotive has three small panels along the lower half of the body on the roof access ladder side, and only one panel on the opposite side.[1]

Series identifying features[edit]

SAR Class 6E1 Series 7 E1884 ID.JPG

The Class 6E1 was produced in eleven series over a period of nearly sixteen years. While some Class 6E1 series are visually indistinguishable from their predecessors or successors, some externally visible changes did occur over the years. Series 1 locomotives had their sandboxes mounted on the bogies, while Series 2 to 11 had their sandboxes mounted along the bottom edge of the locomotive body, with the sandbox lids fitting into recesses in the body.[1]

The Series 6 and Series 7 locomotives are visually indistinguishable from each other, but can be distinguished from all the older series models by the rainwater beading that was added above the small grilles on the sides just to the right of the side doors.[1][3]

Crew access[edit]

The Class 5E, 5E1, 6E and 6E1 locomotives are notoriously difficult to enter from ground level since their lever-style door handles are at waist level when standing inside the locomotive, making it impossible to open the door from outside without first climbing up high enough to reach the door handle while hanging on to the side handrails with one hand only. Crews therefore often chose to leave the doors ajar when parking and exiting the locomotives.[4]

Late model Series 7 locomotives were equipped with side doors on which the outside door latch handle is mounted near floor level, with a simple drawer pull type handle at mid door level. No. E1845 and later locomotives were observed with the lower mounted door handles. No. E1882 is one observed exception with a high mounted door handle, although this may have been the result of a door replacement.[4][5]



When there is no compressed air in the locomotive's system to raise a pantograph to start up, a pantograph hook stick is used to manually raise the pantograph. This starts the high voltage motor that drives the auxiliary alternator to supply 110V power to start the compressor and power other control circuits. Once there is enough main air pressure to keep the pantograph in the raised position, the pantograph hook stick can be dropped.[6]

The locomotive is controlled via resistors over which the voltage is dropped in a configuration of series and parallel electrical circuits. The circuit breakers that switch these circuits work under very high power and voltage and are therefore all pneumatically operated for insulation purposes. Compressed air is required to open or close the switch actions and air is also used for the weakfield cam switch, which also switches under very high currents.[6]


Upon starting off and in the low notches the major part of the voltage is dropped over the banks of resistors and all four traction motors are in series.[6] The blowers that accelerate the dissipation of heat in the resistor banks give the Class 6E1 its very distinctive sound, a deep and loud whine when power is applied.[7]

As the driver notches up, some of the resistor banks are cut out via the pneumatically operated switches and the voltage increases across the traction motors. The more resistors that are cut out as the driver notches higher, the more power is developed by the traction motors. At around 22 to 28 kilometres per hour (14 to 17 miles per hour) the locomotive switches to a parallel combination, where the two traction motors per bogie are in a series electrical circuit while the two bogies are in parallel electrical circuit. Eventually, when all resistors are cut out, the locomotive is operating in full-field.[6]

When the traction motors are operated in full-field, be it in series or parallel mode, they are performing at maximum power for normal operation. To increase the speed at this point, if necessary, higher power output is required from the traction motors. The only way to increase power is to force a higher current flow over short periods. To accomplish this, the weakfield cam switch switches resistance in parallel with the field coils, which reduces the overall resistance of the field coils. This increases the magnetic flux and more power is generated by the traction motors.[6]


The locomotive itself used air brakes, but it was equipped to operate trains with air or vacuum brakes. The brake system would be set up for either air or vacuum train working by means of a turning switch on the driver's brake valve and by pre-setting the appropriate brake valves in the passage.

Compressed air pipes

The Class 6E1 locomotives were built with an air brake system consisting of various valves connected to each other with pipes, commonly referred to as a “bicycle frame” brake system. The compressed air pipes run under the locomotive's belly in a zig-zag pattern, going through bolster and other members to extend its length to allow the maximum amount of moisture to condense on the way to the reservoirs. As a result it has multiple pipe connections. A weakness of the system was that, after an accident or even a hard coupling, these pipes tended to develop leaks at the joints that were extremely difficult to repair.[8]

While hauling a vacuum braked train, the locomotive's air brake system would be disabled and the train would be controlled using the train brakes alone to slow down and stop. While hauling an air braked train, on the other hand, the locomotive brakes would engage along with the train brakes. While working either type of train downgrade, the locomotive's regenerative braking system would also work in conjunction with the train brakes.

When the locomotive was stopped, the air brakes on both bogies were applied together. The handbrake or parking brake, located in Cab no. 2, only operated on the unit's last axle, or no. 7 and 8 wheels.


The Class 6E1 family saw service all over both of the 3 kV DC mainline and branchline networks, the smaller Cape Western network between Cape Town and Beaufort West and the larger network that covers portions of the Northern Cape, the Free State, Natal, Gauteng, North West Province and Mpumalanga.[9]

Reclassification and rebuilding[edit]

Reclassification to Class 16E[edit]

No. E1851 as Class 16E no. 16-410B, Christiana, 22 September 2006

During 1990 and 1991 Spoornet semi-permanently coupled several pairs of otherwise largely unmodified Class 6E1 locomotives, reclassified them to Class 16E and allocated a single locomotive number to each pair, with the individual locomotives in the pairs inscribed "A" or "B". The aim was to accomplish savings on cab maintenance by coupling the locomotives at their number 1 ends, abandoning the number one end cabs in terms of maintenance and using only the number two end cabs. Most pairs were later either disbanded with the locomotives reverting to Class 6E1 and regaining their original numbers, or rebuilt to Class 18E.[9]

Twelve known Series 7 locomotives were part of such Class 16E pairs.[9]

  • E1790 became 16-407B.
  • E1840 and E1841 became 16-409 A and B.
  • E1846 and E1847 became 16-404 A and B.
  • E1848 and E1849 became 16-405 A and B.
  • E1850 and E1851 became 16-410 A and B.
  • E1858 and E1859 became 16-411 A and B.
  • E1870 became 16-406B.

Modification to Class 17E[edit]

No. E1826 as Class 17E, Capital Park, 28 September 2006

Class 17E locomotives were modified and reclassified from Class 6E1, Series 7, 8 and 9 locomotives during 1993 and 1994. Key modifications included improved regenerative braking and wheelslip control to improve their reliability on the steep gradients and curves of the Natal mainline. Unlike the unmodified but reclassified Class 16E locomotives, the Class 17Es retained their original unit numbers after reclassification.[9]

A stumbling block was that the regeneration equipment at many of the sub-stations along the route was unreliable, and since there was no guarantee that another train would be in the same section to absorb the regenerated energy, there was always the risk that line voltage could exceed 4.1 kV, which would make either the sub-station or the locomotive trip out. As a result the subsequent rebuilt Class 18E locomotives were not equipped with regenerative braking.[10]

Fourteen Series 7 locomotives were modified and reclassified to Class 17E, their numbers being E1749, E1775, E1776, E1777, E1778, E1801, E1803, E1805, E1810, E1822, E1826, E1827, E1832 and E1843.[9]

Rebuilding to Class 18E[edit]

Cab 1 of Class 18E no. 18-213, ex Class 6E1 no. E1873, Capital Park, Pretoria, 6 May 2013

Beginning in 2000, Spoornet began a project to rebuild Series 2 to 11 Class 6E1 locomotives to Class 18E, Series 1 and Series 2 at the Transnet Rail Engineering (TRE) workshops at Koedoespoort. In the process the cab at the number 1 end was stripped of all controls and the driver's front and side windows were blanked off in order to have a toilet installed, thereby forfeiting the locomotive's bi-directional ability.[9][10]

Since the driving cab's noise level had to be below 85 decibels, cab 2 was selected as the Class 18E driving cab primarily based on its lower noise level compared to cab 1, which is closer and more exposed to the compressor's noise and vibration. Another factor was the closer proximity of cab 2 to the low voltage switch panel. The fact that the handbrake was located in cab 2 was not a deciding factor, but was considered an additional benefit.[10]

Most of the Class 6E1, Series 7 locomotives that were used in this project were rebuilt to Class 18E, Series 1 locomotives. The known numbers and renumbering details are shown in the table.[10]

Liveries illustrated[edit]

All the Class 6E1, Series 7 locomotives were delivered new in the SAR Gulf Red and yellow whiskers livery. The main picture shows number E1807 in Spoornet maroon livery, passing through Kaalfontein on 23 September 2009. Illustrated below are some of the other liveries that Series 7 locomotives served in.

See also[edit]


  1. ^ a b c d e f South African Railways Index and Diagrams Electric and Diesel Locomotives, 610mm and 1065mm Gauges, Ref LXD 14/1/100/20, 28 January 1975, as amended
  2. ^ "UCW - Electric locomotives". The UCW Partnership. Archived from the original on 12 October 2007. Retrieved 30 September 2010. 
  3. ^ a b Paxton, Leith; Bourne, David (1985). Locomotives of the South African Railways (1st ed.). Cape Town: Struik. pp. 128–129. ISBN 0869772112. 
  4. ^ a b E1882 with high mounted door handle
  5. ^ E1845 with low mounted door handle
  6. ^ a b c d e Operation - South African Classes 6E, 6E1, 16E, 17E and 18E
  7. ^ Dulez, Jean A. (2012). Railways of Southern Africa 150 Years (Commemorating One Hundred and Fifty Years of Railways on the Sub-Continent - Complete Motive Power Classifications and Famous Trains - 1860-2011) (1st ed.). Garden View, Johannesburg, South Africa: Vidrail Productions. p. 297. ISBN 9 780620 512282. 
  8. ^ Information obtained from Transnet engineers and drivers
  9. ^ a b c d e f Railways of Southern Africa Locomotive Guide, 2002 Edition, (Compiled by John N. Middleton), p57, as amended by Combined Amendment List 4, January 2009
  10. ^ a b c d Information gathered from the rebuild files of individual locomotives at Transnet Rail Engineering’s Koedoespoort shops, or obtained from John Middleton as well as several Transnet employees